This invention pertains to a valve for controlling fluid flow, and more particularly to a modulating valve capable of varying the flow rate of fluid in a fluid system.
In a fluid system, such as a heating and cooling system employing a liquid such as water as the heating or cooling medium, conventional two-position prior art valves for controlling flow of fluid in the system provide either 100% flow of fluid in the system or no fluid flow. With this type of valve, temperature output by the heating or cooling system constantly fluctuates in a small range above and below the set point. Valves of this type are desirable for their low cost as well as for their reliability. Further, the configuration of such valves is known to all manufacturers of heating and cooling systems on an OEM basis, and their construction, configuration and operation are familiar, known quantities.
In recent years, modulating valves have been developed to vary the flow rate of fluid in such fluid systems. With a modulating valve, interfaced with modern electronic controllers, a desired output temperature can be maintained relatively stable.
Modulating valves as developed to date generally employ a plunger, or plug, axially movable into and out of an opening associated with a passage, typically the inlet passage, of the valve. The plug is mounted at one end of a stem. The other end of the stem is interconnected with an external actuator arrangement for providing axial movement of the stem, and thereby movement of the plug, relative to the inlet opening. The shape of the plug and the position of the plug relative to the inlet opening control the amount of fluid flowing through the valve.
Prior art modulating valves of this type are expensive due to close tolerances required in manufacture as well as certain high cost components formed of stainless steel or brass. Further, due to the presence of the actuator arrangement and the axial movement of the stem, with the actuator arrangement being located on the exterior of the valve, the valve configuration differs significantly from the known configuration of prior art two-position valves as described.
It is an object of the present invention to provide a modulating valve which is simple in construction and operation, yet which provides the same overall valve configuration as prior art two-position valves. It is a further object of the invention to provide a modulating valve requiring minimal modifications from prior art two-position valves, in order to reduce the manufacturing cost of the valve and to allow the valve to be incorporated into existing heating and cooling systems with minimal changes to the system.
In accordance with one aspect of the invention, a modulating valve includes a body defining an internal cavity and a pair of openings, one of which defines an inlet to the cavity and the other of which provides an outlet from the cavity. An axial passage, defined by one or more walls, extends from one of the openings, preferably the inlet opening. A plug member has a first portion which extends through the inlet opening and into the axial passage, and a second portion disposed within the internal cavity. The plug member first portion includes guide structure which is engageable with the one or more walls defining the passage. An actuator mechanism is interconnected with the second portion of the plug member for controlling the axial position of the plug member relative to the opening. The guide structure cooperates with the one or more walls defining the passage to guide the axial movement of the plug member upon operation of the actuator mechanism. The actuator mechanism includes a pivotable actuator shaft which extends into the internal cavity, and a connection arrangement which interconnects the actuator shaft and the second portion of the plug member, for providing axial movement of the plug member in response to pivoting movement of the actuator shaft. The connection arrangement is preferably in the form of a slot associated with the plug member second portion, and a pin engaged within the slot. A link extends between and interconnects the actuator shaft and the pin, so as to allow the pin to move laterally within the slot relative to the axis of the passage upon pivoting movement of the actuator shaft. In this manner, the plug member is moved axially within the passage. The plug member first portion includes flow-controlling structure which cooperates with the inlet opening, for varying the flow of fluid through the valve body responsive to the position of the plug member relative to the inlet opening. The guide structure is in the form of one or more ribs provided on the first portion of the plug member, with the ribs extending forwardly of the flow-controlling structure.
The invention further contemplates a method of guiding axial movement of a plug member in a valve, substantially in accordance with the foregoing summary.
In accordance with another aspect of the invention, the inlet opening, the outlet opening, and the axial passage which extends from one of the openings, are in axial alignment. The plug member is mounted for movement within the passage, and includes guide structure as summarized above engageable with the one or more walls defining the passage. The plug member is axially movable along an axis coincident with the longitudinal axis along which the axial passage, the inlet opening and the discharge opening are located. The actuator mechanism extends into the internal cavity defined by the valve body, and is laterally offset from the longitudinal axis along which the plug member is movable.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.